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  • 1
    ISSN: 1432-1939
    Keywords: Hydrogen isotope ratio ; Desert ecology ; Water source ; Climate change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seasonal changes in the hydrogen isotope ratios of xylem waters were measured to determine water sources used for growth in desert plants of southern Utah. While all species used winter-spring recharge precipitation for spring growth, utilization of summer rains was life-form dependent. Annuals and succulent perennials exhibited a complete dependence on summer precipitation. Herbaceous and woody perennial species simultaneously utilized both summer precipitation and remaining winter-spring precipitation, with herbaceous species much more reliant on the summer precipitation component. Several of the woody perennials exhibited no response to summer precipitation. Currently, precipitation in southern Utah is evenly partitioned between winter and summer time periods; however, global circulation models predict that summer precipitation will increase in response to anticipated climate change. Our data indicate that components within the community will differentially responde to the change in precipitation patterns. These results are discussed in relation to impact on competition and possible changes in community structure.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: Carbon isotope ratio ; Desert ecology ; Plant community structure ; 13C/12C ; Water-use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Carbon isotope discrimination (Δ) was compared between populations of dominant perennial plant species, differing in life expectancy, in two deserts with contrasting vegetation types. In both deserts, plants of the shorter-lived species showed significantly higher Δ and greater intrapopulation variance in this character compared to the long-lived species. These results indicate underlying differences in gas-exchange physiology, and suggest a positive correlation between water-use efficiency and lifespan in desert plants. Differences in variance for this character may reflect greater microenvironmental variation experienced by shorter-lived plants and/or different forms of selection acting on water-use traits. Spatial distributions were significantly clustered for the shorter-lived species and significantly uniform for the long-lived species, indicating that competition has been important in the development of the long-lived populations. The long-lived Larrea tridentata showed a significant, negative correlation between Δ and Thiessen polygon area, suggesting a positive relationship between water-use efficiency and longevity within this species. This relationship was weakly supported in the other warm desert species, Encelia farinosa, but was not observed within populations of the cold desert species, Gutierrezia microcephala and Coleogyne ramosissima. These results suggest that Δ reflects key aspects of plant metabolism related to lifespan; these differences may ultimately influence interactions among desert plants and the structure of desert plant communities.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1939
    Keywords: Carbon isotope ratio ; Desert ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Population-level variation in the leaf carbon isotope discrimination (Δ) values was examined in Encelia farinosa, a common Sonoran Desert shrub. There was approximately a 2‰ range in Δ values among different plants. These differences in Δ values among neighboring plants were maintained through time, both under conditions when neighbors were present and after neighbors had been removed. Individuals with high Δ values were found to have an accelerated growth rate when these plants were released from competition for water. Individuals with low Δ values were better able to persist through long-term drought. These data suggest possible tradeoffs between conditions favoring high- and low-Δ-value plants within a natural population. Given the temporal variability in precipitation between years and spatial variability in microhabitat quality in the Sonoran Desert, variation in Δ values among E. farinosa plants will be maintained within a population.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1939
    Keywords: Adaptation ; Leaf pubescence ; Leaf reflectance ; Desert ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The performance of coastal and desert species of Encelia (Asteraceae) were evaluated through common garden growth observations. The obectives of the study were to evaluate the roles of leaf features, thought to be of adaptive value (increased leaf reflectance and/or transpirational cooling), on plant growth in the hot, arid, desert garden versus their impact on growth under cooler, relatively more moist coastal garden conditions. E. californica native to the coast of southern California and E. farinosa, and E. frutescens, interior desert species, were grown in common gardens at coastal (Irvine, California) and interior (Phoenix, Arizona) sites under both irrigated and natural conditions. Although all species survived in both gardens during the two and a half year study period, there were large differences in their sizes. In the desert garden, leaf conductance and leaf water potential were both lower than at the coastal site. E. californica shrubs were leafless much of the time under natural conditions in the desert garden and had the smallest size there as well. Under natural conditions, E. farinosa, with its reflective leaf surface, was able to maintain lower leaf temperatures and attained a large size than the other two species in the desert garden. The green-leaved species (E. californica and E. frutescens) were not able to maintain leaves into the drought periods in the desert garden, with the exception of the irrigated E. frutescens which did maintain its leaf area if provided with supplemental watering to maintain transpirational leaf cooling. In the coastal garden, all species survived and there were few clear differences in the physiological characteristics among the three species. E. californica, the coastal native, attained a larger size in the coastal garden when compared with either of the two desert species.
    Type of Medium: Electronic Resource
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